Seeing a message that real-time protection is off — and being unable to switch it back on — can feel alarming. In most cases it has a straightforward cause. Here's how to work through it.

Why Does This Happen?

The most common reasons Microsoft Defender turns off or becomes unresponsive are:

  • A third-party antivirus programme is installed (Defender disables itself to avoid conflicts)
  • A group policy setting is blocking it (common on work computers, less so at home)
  • Malware has deliberately disabled it
  • Windows needs an update
  • A Windows component needs repairing

Fix 1: Check for Another Antivirus Programme

Go to Settings > Apps > Installed apps and look for any third-party security software (such as AVG, Avast, McAfee, or Norton). If you find one you no longer use or didn't intentionally install, uninstall it. Windows Defender will usually re-enable itself within a few minutes of restart.

Fix 2: Restart the Security Center Service

  1. Press Windows + R, type services.msc, and press Enter.
  2. Scroll down to Security Center.
  3. Right-click it and choose Restart.
  4. Also check that Windows Defender Antivirus Service is set to Automatic and is running.

Fix 3: Install Windows Updates

Go to Settings > Windows Update > Check for updates. Install any pending updates and restart your computer. Updates often include fixes to Windows Security components.

Fix 4: Run the Windows Security Troubleshooter

  1. Press Windows + R, type ms-settings:troubleshoot, and press Enter.
  2. Click Other troubleshooters (or Additional troubleshooters on older versions).
  3. Find and run the Windows Security troubleshooter if available.

Fix 5: Repair Windows System Files

Open Command Prompt as administrator (search for cmd in the Start menu, right-click, Run as administrator), then type:

sfc /scannow

Press Enter and let it complete. This repairs corrupted system files that may be preventing Defender from running.

If malware has disabled Defender, a standard scan won't work. Try running a Microsoft Defender Offline scan by going to Scan options in Virus & threat protection and selecting the offline scan. If you still can't get Defender running, ask us — we can help.